The present invention relates to a method of manufacturing a semiconductor device, more specifically, a method of manufacturing a semiconductor device which forms a metal silicide film selectively on a gate electrode and source/drain regions of a MISFET.
In the recent semiconductor devices, in order to suppress the resistance rise of the electrodes to improve the drive performances, generally a metal silicide, which is low resistive, is formed on the electrodes.
Usually, the metal silicide in the electrodes are formed by selectively silicidizing the electrodes by the so-called salicide (self-aligned silicide) process. salicide process is specifically a process of forming a metal film of Ni or others over a substrate surface, reacting, in regions where silicon is exposed, the metal film with the silicon by thermal processing to selectively form metal silicide film and then removing the metal film remaining unreacted with the silicon (refer to, e.g., Reference 1 (Japanese published unexamined patent application No. 2000-091290), Reference 2 (Japanese published unexamined patent application No. 2004-186698) and Reference 3 (Japanese published unexamined patent application No. 2006-128497)).
Recently, the metal silicide is formed by using an alloy of a metal for forming the metal silicide and a noble metal added thereto. Its most advantageous merit is that the noble metal is suitably diffused in the grain boundaries of the metal silicide to thereby form the metal silicide crystal homogeneous, whereby abnormal growth of crystal grains and phase transition can be suppressed.
However, the noble metal material is difficult to be removed with the etchants, such as sulfuric acid hydrogen peroxide mixture (SPM), hydrochloric acid hydrogen peroxide mixture and ammonia hydrogen peroxide mixture (APM), which are usually used to remove the metal film remaining unreacted, and in the process of removing the alloy remaining unreacted, the noble metal remains as residues in the device isolation regions, etc. other than the electrodes and resultantly causes short-circuits between the electrodes.
As a method for removing the noble metal is known to use aqua regia. However, aqua regia is seldom used in the usual semiconductor manufacturing process, and it is essential to incorporate an equipment specialized for the aqua regia. Unless an equipment is specialized for the aqua regia, incidental operations, such as the addition of specifications of the feed and discharge of aqua regia, the tank cleaning, etc., are increased, which is a cause for operational cost increase.